High sea-surface temperatures during the early Aptian Oceanic Anoxic Event 1a in the Boreal Realm
High sea-surface temperatures during the early Aptian Oceanic Anoxic Event 1a in the Boreal Realm
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DOI：
10.1130/g35394.1
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发表时间：
2014-05
期刊：
影响因子：
5.8
通讯作者：
J. Mutterlose;C. Bottini;Stefan Schouten;J. Damsté
中科院分区：
文献类型：
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作者：
J. Mutterlose;C. Bottini;Stefan Schouten;J. Damsté
早期阿普第阶的特点是海洋中广泛发生缺氧，称为海洋缺氧事件（OAE）1a。海底火山高原的强烈脱气可能导致大气中二氧化碳浓度升高，最终导致温室效应。因此，OAE 1a 可以被视为过去的“自然实验”，对于了解气候的未来演变非常重要。然而，OAE 1a 的古温度估计主要基于大量氧同位素，容易受到成岩叠印的影响，而 TEX86 古温度估计的数量有限或来自地层约束较差的剖面。在这里，我们首次基于北中纬度（39°N 古纬度）OAE 1a 剖面的 TEX86 古温度计重建了海面水温 (SST)。我们发现海表温度在 OAE 1a 之前开始上升，并在事件期间达到最大值，海表温度约为 31–34 °C，比来自同一沉积盆地的较古老的 Hauterivian-Lower Aptian 沉积物高 4–9 °C。 OAE 1a 的结束以相对较低的海温（约 30 °C）为标志。这些观察结果得到箭石基氧同位素 (d18OBel) 数据和钙质超微化石的支持。我们的综合数据集清楚地表明，OAE 1a 期间北纬地区盛行“超级温室”条件。海表温度与同时期低纬度地区的海表温度相似，表明早期阿普第阶的特点是气候温暖、纬度梯度减小。
The early Aptian was characterized by the widespread occurrence of anoxia in the oceans, known as Oceanic Anoxic Event (OAE) 1a. Intense degassing from submarine volcanic plateaus presumably resulted in high atmospheric CO2 concentrations, culminating in greenhouse conditions. OAE 1a can, therefore, be considered as a past “natural experiment” important to understand the future evolution of our climate. Paleotemperature estimates for OAE 1a are, however, predominantly based on bulk oxygen isotopes, which are susceptible to diagenetic overprinting, while TEX86 paleotemperature estimates are limited in number or derived from stratigraphically poorly constrained sections. Here we reconstructed for the first time sea-surface water temperatures (SSTs) based on the TEX86 paleothermometer from an OAE 1a section from the middle northern latitudes (39°N paleolatitude). We find a SST rise starting prior to OAE 1a and reaching a maximum during the event, with SSTs of ~31–34 °C, 4–9 °C higher than those of older Hauterivian–lower Aptian sediments from the same sedimentary basin. The end of OAE 1a is marked by relatively lower SSTs of ~30 °C. These observations are supported by belemnite-based oxygen-isotope (d18OBel) data and calcareous nannofossils. Our integrated data set clearly indicates that “super greenhouse” conditions prevailed during OAE 1a at northern latitudes. SSTs are similar to those estimated for coeval low-latitudinal sites, suggesting that an equable warm climate, with reduced latitudinal gradients, characterized the early Aptian.